Enhancing small-scale acetification processes using adsorbed Acetobacter pasteurianus UMCC 2951 on κ-carrageenan-coated luffa sponge.

Background: This study explored the utilization of luffa sponge (LS) in enhancing acetification processes. LS is known for having high porosity and specific surface area, and can provide a novel means of supporting the growth of acetic acid bacteria (AAB) to improve biomass yield and acetification rate, and thereby promote more efficient and sustainable vinegar production. Moreover, the promising potential of LS and luffa sponge coated with κ-carrageenan (LSK) means they may represent effective alternatives for the co-production of industrially valuable bioproducts, for example bacterial cellulose (BC) and acetic acid. Methods: LS and LSK were employed as adsorbents for Acetobacter pasteurianus UMCC 2951 in a submerged semi-continuous acetification process. Experiments were conducted under reciprocal shaking at 1 Hz and a temperature of 32 °C. The performance of the two systems (LS-AAB and LSK-AAB respectively) was evaluated based on cell dry weight (CDW), acetification rate, and BC biofilm formation. Results: The use of LS significantly increased the biomass yield during acetification, achieving a CDW of 3.34 mg/L versus the 0.91 mg/L obtained with planktonic cells. Coating LS with κ-carrageenan further enhanced yield, with a CDW of 4.45 mg/L. Acetification rates were also higher in the LSK-AAB system, reaching 3.33 ± 0.05 g/L d as opposed to 2.45 ± 0.05 g/L d for LS-AAB and 1.13 ± 0.05 g/L d for planktonic cells. Additionally, BC biofilm formation during the second operational cycle was more pronounced in the LSK-AAB system (37.0 ± 3.0 mg/L, as opposed to 25.0 ± 2.0 mg/L in LS-AAB). Conclusions: This study demonstrates that LS significantly improves the efficiency of the acetification process, particularly when enhanced with κ-carrageenan. The increased biomass yield, accelerated acetification, and enhanced BC biofilm formation highlight the potential of the LS-AAB system, and especially the LSK-AAB variant, in sustainable and effective vinegar production. These systems offer a promising approach for small-scale, semi-continuous acetification processes that aligns with eco-friendly practices and caters to specialized market needs. Finally, this innovative method facilitates the dual production of acetic acid and bacterial cellulose, with potential applications in biotechnological fields.

Impact of temperature on gluconic acid production during acetification by Acetobacter aceti.

The current approach to gluconic acid production is acetification at 30°C, a temperature that can be difficult to maintain in tropical countries. This study investigated the production of gluconic acid during acetification by Acetobacter aceti WK at high temperatures. An acid-tolerant and thermotolerant species, A. aceti WK, was used for acetification at three different temperatures, namely, 30°C (normal temperature), 37°C, and 40°C (high temperature). Acetification was performed in a 100 L bioreactor with 0.15% CaCl2 for protection of the cells against high temperatures. The production of the organic acids, that is, acetic acid, gluconic acid, 2-keto gluconic acid, glucuronic acid, citric acid, succinic acid, lactic acid, and formic acid, was analyzed. Under acetification in the target total concentration of 80 g/L, the highest acetic acid content (39.3 g/L) was obtained at 37°C with an acetification rate of 0.3013 g/L/h, while the acetic acid content and acetification rate achieved at 30°C were 31 g/L and 0.3089 g/L/h, respectively. Additionally, gluconic acid presented at the highest concentration of 2.17 g/L. The rate of production of gluconic acid was 0.0169 g/L/h at 37°C. This acetification process at 37°C will be valuable as an alternative source for gluconic acid production for commercial applications.

Increasing the Production of ß-Glucan from Saccharomyces carlsbergensis RU01 by Using Tannic Acid.

In this study, we increased ß-glucan production from brewer's yeast, Saccharomyces carlsbergensis RU01, by using tannic acid. High-pressure freezing and transmission electron microscopy (HPF-TEM) revealed that the yeast cell wall obtained from yeast malt (YM) medium supplemented with 0.1% w/v tannic acid was thicker than that of yeast cultured in YM medium alone. The production of ß-glucan from S. carlsbergensis RU01 was optimized in 3% w/v molasses and 0.1% w/v diammonium sulfate (MDS) medium supplemented with 0.1% w/v tannic acid. The results showed that MDS medium supplemented with 0.1% w/v tannic acid significantly increased the dry cell weight (DCW), and the ß-glucan production was 0.28±0.01% w/v and 11.99±0.04% w/w. Tannic acid enhanced the ß-glucan content by up to 42.23%. ß-Glucan production in the stirred tank reactor (STR) was 1.4-fold higher than that in the shake flask (SF) culture. Analysis of the ß-glucan composition by Fourier transform infrared (FTIR) spectroscopy showed that the ß-glucan of S. carlsbergensis RU01 cultured in MDS medium supplemented with 0.1% w/v tannic acid had a higher proportion of polysaccharide than that of the control. In addition, ß-glucans from brewer's yeast can be used as prebiotic and functional foods for human health and in animal feed.

Increasing the acetification rate of Acetobacter aceti adsorbed on luffa sponge using recycle of incremental oxygenated medium.

Speeding up the production of vinegar from rice wine by acetification, using a packed-bed bioreactor with a luffa sponge matrix (LSM) as adsorption carrier of acetic acid bacteria (AAB), and the effect of oxygenation of the recycled medium were investigated. The 0.06 L/min recycle of medium resulted in a high oxygen-transfer coefficient, while optimal dissolved oxygen (DO) of the medium maximized planktonic AAB cell growth with no contamination due to high acid in an external reservoir without LSM. The highest acetification rate (ETA) of 2.857 ± 0.1 g/L/day was achieved with DO 3.5-4.5 ppm at 35 ± 1 °C. To increase ETA, the optimized oxygenated medium was externally supplied and recycled at the ratio of 0.1. Therefore, acetification was conducted in both the bioreactor and reservoir resulting in an increased ETA (6 ± 0.2 g/L/day). This also aligned with the highest system AAB biomass (confirmed by scanning electron microscopy). Under the recycled oxygenated medium supply consistently high biotransformation yields (average 77.3%) were observed over nine sequential cycles. Meanwhile, an average ETA of 6.3 ± 0.2 g/L/day was obtained. This method can have practical applications in improving the efficiency and speeding up small-scale vinegar production.

Modeling of starter cultures growth for improved Thai sausage fermentation and cost estimating for sausage preparation and transportation.

The purpose of this study was to improve Thai fermented sausage flavor by adding starter cultures (i.e., Pediococcus pentosaceus, Pediococcus acidilactici, Weissella cibaria, Lactobacillus plantarum, Lactobacillus pentosus, and Lactobacillus sakei) as compared with naturally fermented sausage. The predictive mathematical models for growth of P. acidilactici and natural lactic acid bacteria (LAB) in Thai fermented sausage were developed to obtain specific prepared sausage quality. Furthermore, comparisons of sausage preparation and transportation cost between nonrefrigerated and refrigerated trucks were studied. The concentration of 3-methyl-butanoic acid synthesized from LAB inoculated sausage was higher than in the control sample which contributed to the flavor forming. Moreover, the proposed unstructured kinetic models of Thai fermented sausage substrates and products describing the consumption of total protein and glucose, and the production of nonprotein nitrogen responsible for flavor enhancer, lactic acid and formic acid concentration were successfully fitted with two selected experimental data sets of the in situ fermentation of Thai fermented sausage. Finally, the transportation of inoculated sausages in a nonrefrigerated truck by combining fermentation process and transportation was more cost efficient for delivering sausages in a long distance.